Because of the difficulties involved in this or any other mechanical device for controlling the equilibrium, it was in every way advisable to retain in the large machine the Pénaud system, which, though itself imperfect in many ways, had been thoroughly tested in actual flight. In the models, it will be remembered, the combined Pénaud tail and rudder controlled the longitudinal equilibrium by movement in the vertical plane under the combined influence of its initial negative angle and the elasticity of its connection with the frame, the flight being kept as nearly as possible in a straight line by the vertical surfaces of the tail. Although it was necessary that the large aerodrome should be capable of being steered in a horizontal direction, it was felt to be unwise to give the combined Pénaud tail and rudder motion in the horizontal plane in order to attain this end, since the use of it for such a double function might very seriously interfere with its proper action in preserving the longitudinal stability. It was, therefore, at first thought best to dissociate the rudder and tail so that the rudder might be used for horizontal steering without in any way interfering with the proper functioning of the tail. But, as the main desideratum was to obtain a flight of the large machine as soon as possible, and perfection of steering control seemed secondary, it was decided, after further consideration, in order not to risk the unpredictable effects that might result from small changes, to duplicate on the large machine the combined Pénaud tail and rudder of the model, and to add another rudder for steering in the horizontal plane. Constructional requirements determined as the only available position for this rudder a rather disadvantageous one. As will be seen from Plate [53], its efficiency was diminished by its being only about half as far from the center of gravity as the combined Pénaud tail and rudder, and by being located in the lee of a considerable portion of the frame, where it would be subject to the cross-currents of air created by the forward motion of the frame. [p215]
For the preservation of the equilibrium of the aerodrome, though the aviator might assist by such slight movements as he was able to make in the limited space of the aviator’s car, the main reliance was upon the Pénaud tail. But, in the absence of any data for determining the effect produced in passing from the model to the large machine, it could not be certain that calculations based upon the balancing of the model would accurately determine the proper balancing of the large machine. It was therefore decided to provide such attachment for the Pénaud tail that, while it would always have elastic connection with the main frame, yet its angle could be appreciably changed without affecting in any way the degree of elasticity of this connection. After many changes in plans for securing this result, it was finally decided to arrange it in the manner shown in the drawings. Referring to the general plans in Plates [53] and [54], and to the details in Fig. 1 of Plate [56], the main stem of the Pénaud tail is seen to be connected by a pin to the horn (17), which is brazed to the clamping thimble, by which it is mounted on the vertical tube (16), suitably connected and braced to the rear end of the midrod, the horn (17) being larger than the stem of the tail and set at an angle to the vertical tube (16), the pin connection permitting the tail to swing up and down. The bridle (40), connected to the center of the tail on its upper side, passes upward where it is connected to the spring (41), the other end of which is connected to a single wire rope (42), which passes over the pulley mounted on the top of the post (43), which is guyed to the upper guy-post by the wire (44). The wire rope (42), after passing over the pulley, is connected to the spring (45), around the two ends of which it forms a loop, and from there it passes down to the plane of the main frame and through suitable pulley blocks to the aviator’s control wheel (50), which is mounted on the starboard side of the main frame, convenient to the aviator’s right hand when he is facing forward. From this point the wire rope passes through the various pulley blocks towards the rear of the machine, and through the pulley block (46) mounted on the side and near the bottom of the rear lower guy-post. At a short distance beyond this pulley it is connected to a weaker spring (47), the other end of which is connected by a second bridle (48) to the under side of the Pénaud tail at its center. In order to prevent the springs (41), (45) and (47), which furnish the elasticity for the Pénaud-tail connection, from being strained beyond their elastic limit, either by a sudden gust of wind or by the aviator attempting to move so large an area of surface too suddenly, the wire rope (42) was made continuous around the springs, the portion between the points where it was joined to the two ends of the springs being made of such a length as to take the entire strain should the strain on the cord become greater than sufficient to stretch the springs 50 per cent of their original length. [p216]
In the construction of the equilibrium control wheel it was decided that some arrangement must be secured whereby the wheel would normally be inactive and maintain whatever position it had been set to, and at the same time could be moved by the aviator with one hand, the mere act of grasping it rendering it free to be moved, and whereby it must automatically lock itself in any position in which it might be when the aviator removed his hand from it. The multiplicity of things requiring the attention of the aviator made it desirable that his attention to any one of the important details, whether the engine, the equilibrium, or the steering, should never require more than one hand, thus leaving the other hand free either to hold on to the machine or to control some other detail at the same time. While an irreversible wheel, such as would be secured by the use of a worm and worm-wheel, at first seemed likely to answer the purpose, yet the movement of a worm-wheel by means of a worm is necessarily very slow if it is irreversible, and it here seemed desirable to so arrange the wheel that in case of emergency, of for rising or descending, the aviator could swing the Pénaud tail from its extreme upper position to its extreme lower one by a small motion of his hand, and thus small or large adjustments of the Pénaud tail could be intuitively felt to have been produced without the aviator having to remember how many turns he had made of the wheel.
The control of the steering rudder was effected by a steering wheel (51) similar in construction to the equilibrium control wheel (50), a continuous cord (52) passing from the steering wheel through suitable pulleys to either side of the steering rudder (r), springs being interposed in loops in the cord on either side of the steering rudder to give some elasticity to the control apparatus in order to prevent possible danger from the aviator attempting to move the rudder too suddenly. This steering rope passed directly through the steering rudder at the points where it was joined to it; so that, should one side of the cord in any way become entangled with the frame or with its pulleys, the strain produced by the aviator in attempting to move it in the opposite direction would be taken up by the cord and thereby avoid the possibility of destroying the rudder. For even should the cord become entangled on one side, the rudder could be given a slight amount of adjustment through the elasticity of the coiled springs.
The design of the combined Pénaud tail and rudder followed very closely that which had been used for the models, and its area of ninety-five square feet on the horizontal surface with a corresponding area of vertical surface bore the same relation to the area of the tail and rudder of the models that the area of the wings of the large machine bore to that of the wings of its prototype.
While the provisions for automatic equilibrium and manual control were not entirely ideal, even for the quiet atmospheric conditions under which it [p217] was proposed to make the first tests, nevertheless it was and still is believed that the provisions for such conditions were sufficient to enable a successful flight of a few miles to be obtained. It was thought to be very certain that, once a successful flight could be made, the funds for the further prosecution of the work would be readily forthcoming, and that when these funds were obtained the many problems of control, rising and alighting, could be undertaken.
[p218]
CHAPTER VIII
THE EXPERIMENTAL ENGINE
It will be recalled that the contract for the engine for the large aerodrome, which had been entered into on December 12, 1898, called for its completion on February 28, 1899. Between the time when the engine should have been completed and May, 1900, the engine builder had been engaged in a continuous series of changes on it, all connected with what might be briefly called its proper functioning. The actual mechanical construction of the more important parts had been admirably executed, and this main portion of the constructional work had been completed within the time called for by the contract. The trouble was that the engine, which was of the rotary cylinder type, would not furnish anything like the power which had been expected of it, and which the size and number of its cylinders indicated that it should furnish. No one who has not had practical experience in the development of gasoline engines, can understand or appreciate how fourteen months could be spent in changes in the minor details of the engine with the expectation that each contemplated change would bring success; and to anyone who has had experience in the matter, an attempt to explain the delays would merely seem like a history of his own experiences. It is, therefore, sufficient to say that the delay on the engine had now reached a point where it was necessary to bring it to a successful completion immediately or to abandon it definitely, and either find a competent builder who had already built engines which, while not necessarily light, were successful, and who would undertake to construct a light one on the same principles, or, as a last resort, to turn to steam; and even the contemplation of this was appalling.